FINAL INSPECTIONOMPLEMENTATION REPORT FOR THE OFE-POST MAGE TASK ROCKY MOUNTAIN ARSENAL AUGUST 1997

INTRODUM0 The Rocky Mountain Arsenal (RMA) was established in 1942 to manufacture chemical warfare agents and incendiary munitions for use in World War IL Following the war and through the early 1980's, the facilities continued to be used by the Army. Beginning in 1946, some facilities were leased to private companies to manufacture industrial and agricultural chemicals. Shell Oil Company, the principal lessee, primarily manufactured pesticides from 1952 to 1982. Common industrial and waste disposal practices used during these years resulted in contamination of structures, soil, surface water, sediment and groundwater. The RMA Superfund Site is comprised oftwo areal units, On Post and OffPost. The On post unit is encompassed by the boundaries ofRMA; occupying 27 square miles in southern Adams County, approximately 8 miles northeast ofDenver. The OffPost unit is located immediately north ofRMA as shown inFigure 1. The Record ofDecision for the Off-post Operable Unit (12/19/96) for Rocky Mountain Arsenal specified that approximately 160 acres in the southeast portion ofSection 14 and the southwest portion ofSection 13 (Figure 2) would be tilled and seeded with an appropriate seed mix. The objective ofthis project was to thoroughly n-Ax the top 8-10 inches ofsoil through tillage of appropriate areas within the area ofestimated dieldrin concentration greater than 0.04 ug/g, and establish selfsustaining vegetation at those sites.
This project was conducted as a cooperative effort among the Army, Shell and the U.S. Fish and Wildlife Service (the Service). The Army provided fuel for the project. Shell provided project oversight, administrative responsibilities, some equipment, seed and partial labor. The Service provided a large horsepower tractor for pulling the Rotoclear, seed broadcasting equipment and tractor operators. Operator training began on March 1, 1996 and the project work was completed on April 16, 1996. Only minor delays due to inclement weather and equipment maintenance and repair occurred during the project. DESCRIPTION OF BEYEGETATION ACTIVITES The magnitude ofthis project was limited to soil tillage and seeding as detailed in a Task Plan finalized on March 18, 1996. The Task Plan incorporated goals (see Appendix B) by which the

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00005140success ofthe tilling andrevegetation could bemeasured. The soil was tilled and thoroughly mixed to adepth of8-10 inches by aMadge Rotoclear implement pulled by a large horsepower agricultural tractor. Observation ofthe equipment during operation and visual inspection ofthe tilled areas by representatives ofall Parties resulted inagreement that only one pass wasneeded forthorough mixing. Aftertilling, seed wasbroadcast over the soil surface and incorporated into the soil through light harrowing to ensure good soil/seed contact. Two different seed mixes were planted. A diverse native mix (Table 1)consisting ofspecies adapted to the local climate was used for areas around the reservoir and adjacent to the wetland areas bordering First Creek (Figure 2). This site had been over grazed and the vegetation community quite degraded. Species. selected for the native seed mix were included to complement residual vegetation (e.g. inland saltgrass,Wia&Wia stricta) and sand dropseed Sporobolus rvotandius) that would likely volunteer at the site from existing plant material. Because oftheirproximity toFirst Creek, these areas will likely not be disturbed inthe future. The objective forthe areas adjacent to the creek, therefore, was to restore ecologically diverse wildlife habitat. Upland sites were treated differently since future land use aswildlife habitat is less certain. These areas were seeded with amix consisting ofcrested wheatgrass, alfalfa and fourwing saltbush (Table 2). This mix, although less diverse, consists ofspecies easily established that will stabilize soilsforthe long term while providing some habitat suitability during the open space nature ofthe site.

Table 1. Seed Mix forTilled Areas Adjacent to First Creek Lbs. PLS/ Scientific Name Common Nam Variet Acre* Pasco=on smitWi Western Wheatgrass Arriba 7.6 Panicurn virgatum Switchgrass Nebraska 28 1.2 Elyms canadensis Canada Wildrye Native 3.5 Gaillardia aristata Blanket Flower Native 0.1 Unum lewisfi BlueFlax Native 0.1 Helianthus amms Annual Sunflower Native 0.1 Achillea lanulo Yarrow Native 0.01 Ratibida columnifera Prairie Coneflower Native 0.1 DiLp-a puipu Purple Prairie Clover Native Total 12.81 *Lbs.PLS/Acre = pounds ofpure live seed per acre

2Table 2. Seed Mix forUpland Tilled Areas Lbs. PLS/ ScientificName Common Name Vangty Acre* Aero=on cristatum Crested Wheatgrass Hycrest 9.0 Atriplex canescens Fourwing Saltbush Native 0.2 Medicaizo afim Alfalfa Ladac 1.5 Total - 10.7 *Lbs.PLS/Acre = pounds ofpure live seed per acre

STATUS QEREVEGETATION Visual inspection ofthe sitewas conducted monthly after seeding was completed on April 16, 1996. Although different seed mixeswere used in the twopotential future land use zones, each zone responded similarly. In October, 1996 vegetation dominating the entire site consisted of plants that volunteered from existing plant material that survived the tilling process or plants that grewfrom seed that existed in the soil seed bank. Seedlings ofseeded species were not as noticeable, although these could befound with attentive inspection. Crested wheatgrass, alfalfa and weedy perennial and annual forb species occurred in theupland site, while inland saltgrass and weedyperennial and annual forbs re-established inthe lower areas. Basedupon experience gained through revegetation efforts over the past eight years in the Onpost Operable Unit, results observed in the OffPost areawere notunexpected. Dramatic establishment and growth ofseeded speciesusually does not occur during the first growing season. In this case, two factors were primarily responsible for the observed result. First, existing, more mature plantmaterial has a competitive advantage over seedlings and usually dominate revegetation efforts when present. Secondly, climatic conditions occurring in the months following seeding were not conducive to extensive seedling growth. Precipitation was low fornearly all months ofthe growing season (Table 3). The month ofMay had average precipitation, butthe moisture mainly came at the end ofthe month when temperatures were high so that effective precipitation was low. The distribution ofprecipitation post seeding certainly promoted establishment and growth ofthe weedy warm season species kochia. Because ofthe height and density ofthis species, most ofthe site was mowed mid-summer to prevent shading of desirable seedlings.

3Table 3. Inches ofprecipitation/percent oflong term average (1948-1995) recorded at the National Weather Service Denver field office for months following seeding ofthe off-post area in 1996. April May* June July August September NWS** 0.48 2.73 1.58 1.22 0.26 NA (27%) (108%) (93%) (66%) (18%)

0.31 2.29 1.13 0.86 0.42 2.46 (18%) (91% (67%) (47%) (420/-) (218%)
Note that more than 80% ofthis months total came during the last 8 days ofthe month. **Data from theNational Weather Service Denver field office ***Data from a monitoring station at the Shell Trenches site at Rocky Mountain Arsenal. One problematic effect ofthe tillage program isthat Canada thistle, a noxious weed species, became widely re-established over the site. Since Shell acquired the property in 1991, considerable effort hasbeen expended to control established populations of this troublesome plant species. Significant effort will again be required to prevent Canada thistle populations on Shell property from becoming a nuisance to adjoining agricultural and housing development land. Goals stated in the task plan for this project were for establishment ofa minimum average ofone perennial grassland species per square meter with no visible soil erosion within the tilled area. Both visual inspection and quantitative estimates ofperennial plant density and annual plant cover (Table 4) indicate that goals have been met. There is no evidence ofsoil erosion, i.e. there are no rills indicating erosion by water or wind deposited/eroded soils. Although the plant community is still developing, there is sufficient plant cover to prevent any erosion developing overwinter. Confirmation ofthese observations was made by representatives ofthe Parties during the final inspection ofthe site which occurred on October 17, 1996. Two types ofvegetation datawere collected to verify visual observations. Individual plants were counted in randomly placed 1-square meter quadrats to estimate perennial plant density forthe site, and insure that the goal ofone perennial plant per square meter was met. In addition, total coverby annual species was estimated as further indication ofsoil stabilization. Cover by annual species was the selected metric because it was not practical to count the numerous annual individuals. Average perennial plant density for the native seeded area was approximately 29 and 10 for the upland seeded area (Table 4). These values are well above the goal set for the project. In addition, mean cover by annual species was 29 percent forboth the native area and the upland locations (Table 4). In combination, these values indicate that vegetation is well established in 4tilled areas ofthe Off:-post Operable Unit.

Table 4. Summary Statistics forPerennial Plant Density and Annual Plant Cover EstimatesBased onData from Randomly Placed I-square meter Quadrats. Native Seeded 

### AM Upland Seeded Am Number ofquadrats 38 72 Mean number ofperennial plants 29.4 9.8 Standard Deviation 36.2 12.1 Range 0-127 0-87 Mean percent annual plant cover 28.9 28.8 Standard Deviation 14.9 21.8 Range 5-60 5-90
RECOMNHIbMATIONS FDR MAINTENANCE ACTFVIM-S Maintenance ofthetilled areawill be conducted by Shell, owners oftheproperty. Maintenance activities will include butnot be limited to: control ofnoxious plant species and other weedy plant speciesthat may interfere with establishment ofself-sustaining vegetation and re-seeding areas that failed to establish. Specific maintenance operations that willbe conducted during the fall of1996 and during 1997 include control actions targeting Canada thistle populations and mowing annual weedy species, especially kochia,to promote establishing desirable species. Overseeding areas withlittle establishment ofperennial grasses may be suggested for fall 1997 ifan additional growing season does not produce suitable results. LESSONS LEARNED 1. Established perennial vegetation, especially crested wheatgrass, inland saltgrass and field bindweed, has ahighprobability ofre-establishing after a single tillage regardless ofhow thoroughly the soil is tilled at that time. Many habitat improvement projects to be conducted On Post atRMA have thegoal ofchanging crested wheatgrass stands into more diverse habitats. It willbe necessary to conduct additional control beyond a single tillage to eliminate established plants prior to seedingwith adiverse native seed mix. 2. TheMadge Rotoclear thoroughly mixed soils after onepass ofthe implement, and itsmassive power allowed tilling without any pre-clearing ofexisting vegetation. However, the intensive maintenance that theimplement requires, the large quantity offuel consumed, and the limited depth to which soils canbe tilled mayindicate that use ofa deep plowing agricultural disc maybe
5more efficient for mostuses at RMA. The rotoclear would be most useful in areas such as shrublands where considerable clearing ofvegetation would be necessary before working soil. PROJECTCOSTS The total cost estimated for the combined efforts ofthis project was $60,000. This amount includes labor estimates, equipment rental, material cost and contingency. Actual cost ofthe project was less as indicated below. Labor: $18,247 Equipment: 17,794 Small tools/consurnables (Fuel): 1,415 Materials: 7,008 Fees/Distributable: §J31 Total 51,001

PROJECT SUMMARY Following the pre-final inspection held at the OffPost unit on April 26, 1996, only growth ofthe seeded areas had not occurred. All other activities, as mandated by the ROD and detailed inthe Task Plan, had been completed. By the time ofthe final inspection on October 17, 1996, adequate growth ofthe seeded areas had occurred as documented inthis report. This phase of the OffPost remedy was a comprehensive "one-time correction" and does not require active operation and/or maintenance other than routine vegetation maintenance to ensure compatibility with surrounding land use. No modification ofthe activities delineated in the TaskPlan was required to complete this project. There are no outstanding construction items remaining from the pre-final inspection. CERTMCATTON Ihereby certify that the construction activities as identified in this document were performed in accordance with the OffPost Record ofDecision and the "Task Plan for Tilling and Revegetation of160 Acres ofthe OffPost Area."

-'Mr. Charles T. Scharmann

Remedy Execution Manager

6CHRONOLOGY 01EYENTS December 19, 1995 Record ofDecision signed February 14, 1996 Meeting ofall Parties to review Task plan February 20, 1996 Draft Task Plan mailed to all Parties March 4, 1996 Operator training March 11, 1996 Site visit by all Parties March 18, 1996 Revised Final Task Plan mailed to all Parties Tilling initiated Public notice ofavailability ofTask Plan forreview March 29, 1996 Mid-point site visit byall Parties April4, 1996 Public meeting forreview/update ofproject April 15, 1996 Tilling completed April 16, 1996 Seeding completed April 18, 1996 Draft Pre-final Inspection Report sent to all Parties April26, 1996 Pre-final inspection conducted October, 1996 Draft Final Inspection Report October 17, 1996 Final Inspection conducted January 17, 1997 Draft Final Task/Implementation Report June 6, 1997 Final Inspection/implementation construction report

7Appendix A: Pre-final Inspection Report

8

### PRE-FINAL IINSPECTTON REPORT

EM-ODUCTION TheRecord ofDecision forthe Off-post Operable Unit (12/19/96) forRocky Mountain Arsenal specified thatapproximately 160 acres inthe southeast portion ofSection 14 and the southwest portion ofSection 13 would betilled and seeded. The objective ofthis projectwas tothoroughly mixthe top 8-10 inches ofsoilthrough tillage ofappropriate areas within the area ofestimated dieldrin concentration greater than 0.04 ug/g, and establish -self sustaining vegetation atthose sites. Tilling was conducted using a rotoclear which is alarge rototiller type implement. An appropriate seed mixwasbroadcast over tilled areas and harrowed to insure good soil/seed contact. This project was conducted as a cooperative effort among theArmy, Shell and theU.S. Fish and Wildlife Service (the Service). The Army provided fuel forthe project. Shell provided project oversight, administrative responsibilities, some equipment, seed and partial labor. The Service provided a large horsepower tractor forpulling the rotoclear, seedbroadcasting equipment and tractor operators. Theproject was initiated with operatortraining on March 1,1996 and was completed onApril 16, 1996. Theworkperiod included minor delays due to inclement weather and equipment maintenance and repair. Thetilled areas will bevisually monitoredto detect any large areas (i.e., areas greater than 0.01 acres) where revegetation hasfailed. Areas ofthis size thatfail to revegetate willbe re-seeded in September, 1996. DESCRIPTIONDE AGRICULTURAL ACTBn=S Activity forthis project was limitedto soiltillage and seeding. The soil was tilled andthoroughly mixed to a depth of8-10 inchesby a rotoclear implement pulledby a largehorsepower agricultural tractor. Only onepass wasneeded forthorough mixing. Aftertilling, seedwas broadcast overthe soil surface and incorporated into the soil through light harrowing. Two seed mixes wereused for this project. Adiverse native mix consisting ofspecies suitable forlower topographic positions with higher soil moisture was used for areas around the reservoir and adjacent to FirstCreek. These areas will likelynot bedisturbed in the future. Upland sites where future land useisunknown were seeded with amix consisting ofcrested wheatgrass, alfalfaand fourwing saltbush. This mix will stabilize soils forthe longterm whileproviding adequate habitat diversity duringthe open spaceuse ofthe site. DISCUSSION DEMAINTENANCE REQUrREMENTS Maintenance ofthetilled area will be conducted by Shell, owners ofthe property. Maintenance
9activities will include but not belimited to: control ofnoxious plant species and other weedyplant species that may interfere with establishment ofself-sustaining vegetation and re-seeding areas thatfail to establish. FINAL INSPECTION DOCUMENTATION Apre-final inspection will be scheduled for theweek ofApril 22, 1996 and final inspection will occur in September, 1996 after vegetation has been established and/or failed areas havebeen reseeded. SUMMARY Of PROJEC COSTS A summary ofproject costs willbe provided withthe Final Task Report due inNovember, 1996. CHRONOLOGY DE EVENTS December 19, 1995 Record ofDecision signed February 14, 1996 Meeting ofall Parties to review Task plan February 20, 1996 Draft Task Plan mailed to all Parties March 4, 1996 Operatortraining March 11, 1996 Site visit by all Parties March 18, 1996 Revised Final Task Plan mailed to all Parties Tilling initiated Public notice ofavailability ofTask Plan forreview March 29, 1996 Mid-point sitevisit by allParties April 4, 1996 Public meeting for review/update ofproject April 15, 1996 Tilling completed April 16, 1996 Seeding completed April 18, 1996 Draft Pre-final Inspection Report sent to all Parties April 26, 1996 Tentative date forpre-final inspection August, 1996 Draft Final Inspection Report September, 1996 Final Inspection November, 1996 Final Task Report

10Appendix B: Task Plan for Tilling and Revegetation of 160 Acres ofthe Off-Post AreaTASK PLAN FOR TILLING AND REVEGETATION OF 160 ACRES OF THE OFF-POST AREA

Task Description The Agreement for a Conceptual Remedy for the Cleanup ofthe Rocky Mountain Arsenal and the Record ofDecision forthe Off-post Operable Unit (12/19/95) specified that approximately 160 acres in the southeast portion ofSection 14 and the southwest portion ofSection 13 would be tilled and seeded. Although a total of 160 acres will betilled during this project, the tilling will not be contiguous because wetlands, tree groves and other areas will not be included, as described in a letterto JeffEdson, CDPIHE (attached). Soil inthe project area will be tilled and thoroughly mixed to a depth ofabout twelve inches. The area will then be seeded with a n-dx ofappropriate plant species to protect soil from erosion and establish a self-sustaining plant community.

Site Description The site is located immediately north ofRocky Mountain Arsenal (Figure 1). The terrain is generally flat with slopes no greater than 5%. Soils are loam, sandy loam or wet to moderately wet alluvial material. Vegetation types include areas that have been seeded with exotic grassland species, degraded sites with a variety ofweedy and native grassland species, planted tree groves, and wetland sites. In addition there is a groundwater treatment facility with treatment plant and extraction and injection wells, and buildings from a previous home site (Figure 2).
Objective The objective ofthis project is: To thoroughly mixthe top 8-10 inches ofsoil through tillage ofappropriate areas within the area ofestimated dieldrin concentration greater than 0.04 ug/g, and establish self sustaining vegetation at those sites (Figure 3).

Goals 1. At the end ofthe first growing season following tilling, on average, a minimum ofone perennial grassland species per square meter will be established. 2. Also at the end ofthefirst growing season, there will be no visible soil erosion anywhere within the tilled area.

12Itis necessary forthis project is to produce a selfsustaining plant community established in a timely manner after tilling. This plant community can be composed ofplant species that are expected to volunteer from plant materials already on site or species that are being seeded during the project. Soils will be stabilized by live plants or by mulch incorporated into the soil. After the first growing season, the established plant communities will develop an appearance similar to comparable grasslands in the region. The rate ofthis development will be dependant upon climate, but will be enhanced to the extent possible by maintenance activity such as weed control and mowing.

Methods Soil tilling and mixingwill be conducted with a specialized "industrial" type machine called a rotomill or rotoclear. The device was initially developed to remove the top ofasphalt roads before resurfacing. The technique was modified by the coal mining industry to prepare mountain shrublands and forested areas for direct haul salvage oftopsoil. Therotoclear is pulled by a large horsepower tractor. Atoothed drum rotating at a relatively high rate incorporates all standing biomass into the soil at a depth of 12 inches. The result is a thoroughly mixed profile to the 12 inch depth. Grassland seed mixtures would then be broadcast seeded and incorporated into the soil by harrowing the soil surface.
Responsibilities Shell will provide project oversight, all materials required, a small tractor for conducting broadcast seeding and harrowing, and an operator for seeding and harrowing operations. Shell will also lease the rotomill for use during this project. Following completion and final inspection ofthe project, Shell will assume responsibility for producing a taskreport that will contain an introduction, chronology ofevents, discussion ofprogress toward meeting revegetation goal, final inspection documentation, certification that the project was effective, maintenance recommendations, and a summary ofcost. The Service (U. S. Fish and Wildlife Service will provide a large horsepower tractor for pulling the rotomill andtractor operator for the duration ofthe project (10-14 days) and seed broadcasting equipment. The U. S. Army, EPA and State will participate in prefinal and final inspections ofthe site. An initial inspection will be scheduled soon after tillage isinitiated in order to obtain concurrence with the method by allparties before a large amount oftillage has occurred. A final inspection willbe scheduled after all tilling and seeding has been conducted. Subsequent inspection maybe scheduled to monitorthe progress ofplant community development.

13Potential Impacts to Communities No impacts are anticipated to nearby communities through conducting thisproject. The activity is simply soil tilling followed by broadcast seeding ofgrassland plant species. It is not different from concurrent farming activity on adjacent properties. Noise, traffic or dust levels will not increase detectably. The only noise associated with this project isthat produced by operation ofafarm tractor andthe rotocleartiller. These will not operate near residential areas. Only two orthree people are required for implementation ofthe project. No other trafficis associated. Dust emissions are not anticipated to be aproblem. Adequate soil moisture while the activity isbeing conducted andincorporation ofa considerable amount ofexisting standing vegetation into the tilled area as mulch will prevent deflation ofsoil particles. -Thus dust emissions will be minimized. In the unlikely eventthat excessive amounts ofdust are produced, a dust suppressant willbe applied. Community Relations/Notification The importance ofcommunity relations activities to keep communities informed ofsite actions has been recognized through a variety ofnotification and discussion. Officials in the government ofCommerce City and the Tri-county Health Department, as well as all adjacent land owners have been notified ofthe pending tilling and revegetation activity. Although a specific taskplan was not complete at the time,the agreement to revegetate 160 acres ofthe offpost area was briefly discussed at public meetings held in conjunction with theConceptual Remedy and Proposed Plan documents. The task plan is simply a presentation ofstandard tillage and revegetation activities and does not differ significantly from the plan presented during those public meetings. In addition, there has notbeen a request to hold apublic meeting to specifically discuss this minor component ofthe offpost Record ofDecision; however, ifarequest ismade, apublic meeting will be held. An additional effort to keep the public informed about this activity will include publishing information about the project in the newsletter thatthe Army sends out to local and interested citizens.

Health and Safety Work will be performed under existing Project Health and Safety plans, as well as a project specific plan (attached) which will address considerations unique to operation ofthe rotomill, and contingency plans specific to this project. These plans willbeprovided by Shell. The owner of the roton-dll (Monarch and Associates) will conduct a training session priorto operation ofthe rotomill.

14Cost Estimate Total cost estimated for the combined efforts of this project is $60,000. This figure includes labor estimates, equipment rental and seed cost, equipment use cost and contingency.

Schedule Preferred starting date: March 1, 1996 (or sooner ifweather conditions and logistics allow) Preferred completion date: Start date plus 20 work days or sooner Draft pre-final inspection report: Completion date plus I work day Pre-final inspection: Completion date plus 5 work days or sooner Draft final inspection report: 30 days prior to Final Inspection Final inspection: September, 1996 Final Task Report 60 days following final inspection

15

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